Omake is a small free gift(it's hard to explain...somebody help me!).
A few weeks ago I bought a bottle of apple juice.It came with one of the characters from "ONE PIECE" (Japan's NO.1 manga in recent years)on a small mobile phone strap.
It's a promotion for boosting sales,one of many in Japan where choices are many and competition high.
In this case the juice company is using the huge popularity of "ONE PIECE"and timing their promotion to coincide with the soon to be released movie version.
It was a huge success the product was sold out with in a few days.

